High maternal physical activity levels during the second trimester were associated with lower body fat percentage in female neonates but not male neonates, suggesting sex-specific effects of prenatal exercise on infant body composition.
A significant sex difference in neonatal body fat percentage was observed, with male infants averaging 11.7% and female infants averaging 13.0%.
High maternal physical activity during the second trimester was associated with lower body fat percentage in female infants when measured by the IPAQ questionnaire.
High maternal physical activity during the second trimester was also associated with lower body fat percentage in female infants when measured by the Godin Leisure-Time Exercise questionnaire.
No association was observed between high maternal physical activity during the second trimester and body fat percentage in male infants.
The study utilized data from the Western Australian ORIGINS birth cohort, including 323 pregnant women and their infants born between 2016 and 2024.
This research suggests that how physically active a mother is during the second trimester of pregnancy may influence how much body fat her baby has at birth, and that this effect differs depending on the baby's sex. Among 323 mother-infant pairs from a Western Australian birth cohort, mothers who were more physically active during the second trimester had daughters with notably lower body fat percentages at birth — roughly 1.7 to 3.2 percentage points lower — but no similar relationship was found for sons. Female newborns also had slightly higher body fat on average (13.0%) compared to male newborns (11.7%). The study used two different questionnaires to measure physical activity and confirmed the findings with both, strengthening confidence in the results. Body fat in newborns was measured precisely using a specialized device called a PEA POD, which uses air displacement to assess body composition within the first week of life. The fact that the association appeared only in female infants points to possible biological differences in how male and female fetuses respond to their mother's exercise habits during pregnancy. This research suggests that promoting physical activity during pregnancy could have benefits for newborn body composition, particularly for female infants, and supports the idea that prenatal care recommendations around exercise may need to account for fetal sex. The authors note that more research is needed to understand what other factors shape infant body fat, which could help refine guidance for expectant mothers.
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Upload Your LabsEinarsdottir K, Bear N, Sogutluoglu A, Silva D, Gibson L. (2026). Associations between second-trimester maternal physical activity and neonatal body composition: findings from the ORIGINS birth cohort.. Journal of developmental origins of health and disease. https://doi.org/10.1017/S2040174426100750